Surveillance systems are being used with increasing frequency to detect and track individuals within an environment. In security applications, for example, such systems are often employed to detect and track individuals entering or leaving a building facility or security gate, or to monitor individuals within a store, hospital, museum or other such location where the health and/or safety of the occupants may be of concern. More recent trends in the art have focused on the use of facial detection and tracking methods to determine the identity of individuals located within a field of view. In the aviation industry, for example, such systems have been installed in airports to acquire a facial scan of individuals as they pass through various security checkpoints, which are then compared against images contained in a facial image database to determine whether an individual poses a security threat.
Current facial detection and tracking systems typically rely on the use of one or more pan-tilt-zoom (PTZ) cameras to track individuals located within a wide field of view. Such devices can include an optical system operatively coupled to a number of drive motors that permit the operator to zoom-in on the details of an individual, or to monitor a larger area from multiple camera angles. In certain designs, each of the cameras within the system can be connected to a computer equipped with image processing software and/or hardware that can be used to process images received from the cameras in order to detect the identity of the individual.
Due to the high resolution often necessary to accurately detect facial features, many prior-art facial detection and tracking systems lack the ability to both detect and track individuals within a wide field of view while simultaneously acquiring information sufficient to perform facial recognition. In systems employing PTZ cameras, for example, the ability of the camera to effectively track motion within a wide field of view is often limited by the speed and accuracy of the positioning mechanism employed. If, for example, the individual is located within a moving vehicle or is otherwise moving quickly through the image field, such cameras may not be able to adequately cover the entire image field while still providing sufficient resolution to abstract features from the individual's face. In some cases, the inability of the camera to accurate track individuals moving through the image field can also prevent multiple individuals from being detected and/or tracked simultaneously within a wide field of view.